吃素比吃肉更环保？先得要吃对了才行

03 吃素比吃肉更环保？先得要吃对了才行

生产蔬菜食物造成的碳排放量，一定比肉类的低吗？

据一家中国主流媒体，一家德国媒体报道称，随着富裕程度的提高，中国人餐桌上的肉类正在不断增加。位于旧金山的环保组织野生救援协会发布了这样的数据：2015年中国人均肉类消费量为63千克，生产这些肉类产生的人均温室气体，其升温效应相当于876千克二氧化碳。近年来中国人饮食结构发生改变，吃肉量增大导致全球变暖？

网友们纷纷表示不服：这个锅我们中国人可不背，要说饮食结构，西方国家的人们才是真正的“肉食动物”呢——

@Teddy要去UK：德国人天天吃香肠我们说什么了。

@Claude-Monet：拿肉当饭吃的认为拿肉当菜吃的吃肉太多？

（来源：Weibo.com）

不过，姑且不去讨论中国人饭碗里的肉食是不是影响了世界气候，人们都是越来越相信：畜牧业是全球温室气体排放的重要来源之一。

据Wikipedia：

Due to the significant contribution of agriculture to the emissions of non-CO2 greenhouse gases, such as methane and nitrous oxide, the relationship between humans and livestock is being analyzed for its potential to help mitigate climate change.Strategies for the mitigation include optimizing the use of gas produced from manure for energy production (biogas).

农业是非二氧化碳温室气体（如甲烷和一氧化二氮）排放的重要来源。为此，人们正在分析人类和牲畜之间的关系，以寻求减缓气候变化的潜在方法。其策略包括，最大化利用动物粪便产生的沼气来发电等。

《国际财经时报》（International Business Times）指出，甲烷的温室效应远高于二氧化碳，而畜牧业产生着惊人的甲烷排放量：

A new study of methane emissions finds that the U.S.is spewing 50 percent more methane, a greenhouse gas 21 times better at trapping heat than carbon dioxide, into the atmosphere than the Environmental Protection Agency previously assumed.

一项最新的甲烷排放研究发现，美国的排放到大气中的甲烷量比环境保护署此前预测的高出50%。甲烷的温室效应是二氧化碳的21倍。

A single cow can produce between 250 and 500 liters, or about 66 to 132 gallons, of methane a day (the average U.S.vehicle gas tank can hold about 16 gallons of gas).

一头牛每天可以产生250到500升（合66到132加仑）甲烷。而平均美国汽车油箱可以装载16加仑甲烷。

英国《卫报》之前就曾经刊登这样一篇文章：

Eat less meat to avoid dangerous global warming, scientists say

科学家称：减少食肉量可避免全球变暖

里面是这样说的：

Growing food for the world's burgeoning population is likely to send greenhouse gas emissions over the threshold of safety, unless more is done to cut meat consumption, a new report has found.

一项最新的研究发现，世界人口迅速增长，食物量也随之增加，这似乎正将温室气体排放量推着超过安全线，除非人们减少肉食的消费。

A widespread switch to vegetarianism would cut emissions by nearly two-thirds, it said.

这项研究称，普遍选择吃素有望将温室气体排放量减少近三分之二。

In three decades, emissions related to agriculture and food production are likely to account for about half of the world's available “carbon budget”-the limited amount of carbon dioxide and its equivalents that can be poured into the atmosphere if we are to hold global warming to no more than 2C.

三十年内，农业和食物生产相关的温室气体排放有可能占全世界“碳预算”中的一半。所谓“碳预算”，即为了达到全球气温增长控制在2摄氏度以内这个目标，排放到大气中的二氧化碳和二氧化碳当量气体的上限值。

While energy generation, transport and buildings have long been a target for governments, businesses and campaigners looking to reduce emissions, the impact from food production has often been left out.But on current trends, with intensive agriculture increasingly geared towards livestock rearing, food production will be a major concern.

政府、商界和活动人士在寻求减少温室气体排放时，一直以来都把目标锁定在能源开采、交通运输和建筑方面上，常常忽视了食物生产对全球变暖的影响。不过按照目前的趋势，农业与家畜饲养联系日益紧密，食物生产将会变成一个主要的忧虑。

不过吃蔬菜真的会比吃肉“更环保”吗？BBC带来的观点是：考虑到不同类型食物对人体供能的效果是有差异的，吃蔬菜带来的温室效应可能更大。

Farming, production in factories and transport of goods are all largely powered by the burning of fossil fuels, generating greenhouse gases that trap heat in the atmosphere.Scientists measure this impact as a “carbon footprint”, commonly expressed as the volume of carbon dioxide produced per 100g serving of food.

农耕、工厂生产、货物运输的驱动都依赖化石燃料的燃烧，这些过程产生了温室气体，将热量储存在大气中。科学家们用“碳足迹”来衡量这种影响，通常表示成，生产每100克食物所排放的二氧化碳体积。

This approach, however, doesn't consider how much energy our bodies get from those foods.You need to eat a far greater weight of lettuce to get the same number of calories as a slice of cheese, for instance-with one study finding that it would release three times as many greenhouse gases to provide the same nutritional energy.Processed vegetables, or those imported from distant farms, may fare even worse.

不过这样的方法并没有考虑到我们的身体从那些食物中获得了多少能量。譬如，若想获得和一片芝士相同的热量，你需要吃掉更多重量的生菜——一项研究发现，要提供同样的营养能量，生产这些生菜将要排放出三倍于芝士的温室气体。加工蔬菜或者来自遥远农场的进口蔬菜恐怕带来的碳排放更糟糕。

In a paper in the American Journal of Clinical Nutrition, Adam Drewnowski at the University of Washington in Seattle and colleagues tried to take this into account by estimating the carbon emissions for every 100 calories of different foods.

在一份发表在《美国临床营养学杂志》的论文中，来自西雅图华盛顿大学的Adam Drewnowski和他的同事试着将热量这一点纳入考量，估算生产100卡路里不同的食物造成的碳排放。

（你吃的每100卡路里面包，约产生50g二氧化碳）

（你吃的每100卡路里肉类，约产生248g二氧化碳）

（你吃的每100卡路里牛奶，约产生351g二氧化碳）

（你吃的每100卡路里鸡蛋，约产生440g二氧化碳）

（你吃的每100卡路里蔬菜罐头，约产生787g二氧化碳）

因此，即便是为了健康和环保而奉行素食主义，也应该尽量选择本地蔬菜，少吃加工蔬菜。

词汇总结

mitigate ['mɪtɪgeɪt]

v.使缓和，使减轻

The relationship between humans and livestock is being analyzed for its potential to help mitigate climate change.人们正在分析人类和牲畜之间的关系，以寻求减缓气候变化的潜在方法。

burgeoning ['bə:dʒəniŋ]

adj.迅速成长的; 迅速发展的

threshold ['θreʃəʊld]

n.门槛; 〈喻〉开始

Growing food for the world's burgeoning population is likely to send greenhouse gas emissions over the threshold of safety.

世界人口迅速增长，食物量也随之增加，这似乎正将温室气体排放量推着超过安全线。

livestock rearing 家畜饲养

gear [gɪə]

v, (使)搭配; (使)适合

Intensive agriculture increasingly geared towards livestock rearing.

农业与家畜饲养联系日益紧密